Flail type manure spreaders were first disclosed in Elwick U.S. Pat. No. 2,886,332. Such spreaders have a container which is essentially a semi-cylindrical tank with upright end walls, and a longitudinal shaft on the axis of the cylinder carries flexible flails which fling the contents over a side of the container which is called, for convenience, the discharge side. The opposite side of the container is herein referred to as the rear side; and movement of an element between the discharge side and the rear side is termed "fore-and-aft" movement. The foregoing terminology is used only for convenience of definition in the present application, because the discharge side of the container may be to one side of the path of travel of the spreader, or may be transverse to the path of travel and at the rear with respect to the direction of movement.
All flail type spreaders require some sort of shield or hood which extends upwardly from the rear side of the container and toward the discharge side so as to direct material flung by the flails over the discharge side. It has been found that such spreaders perform better with a shield or hood which has its free edge pretty close to the vertical plane of the discharge side of the container, and this requires that at least part of the hood be moved away from the discharge side to facilitate loading of the container which is most commonly done from the discharge of a barn gutter cleaner or by means of a front end loader.
Most prior art flail type spreaders have a hood which includes a fixed portion along the rear side of the container and one or more hinged portions which may be swung back for container loading. Such a structure is disclosed in Hodgson U.S. Pat. No. 3,856,210.
A different approach is found in Wilkes et al U.S. Pat. No. 3,121,568, in which a hood which is approximately one quarter of a cylinder is hinged along the rear side of the container and pivoted outwardly and upwardly around the hinge. In this apparatus the flail shaft is journalled in the end walls of the hood, and thus swings out of the way for loading.
A third approach is that of Wood U.S. Pat. No. 3,294,406, in which the hood has vertically spaced rollers outside its end walls which ride above and below complementary inturned tracks which extend fore and aft along the top edges of the container end walls. In the Wood construction, the hood translates horizontally away from the discharge side of the container to a loading position in which it straddles the rear side of the container.
While all of the above described constructions are perfectly satisfactory for their intended purposes, each of them presents practical problems in operation. In the first place, it is sometimes necessary for a flail type manure spreader to be moved into a filling location which has relatively little vertical clearance, so any movement of the hood which increases the overall height of the unit may create problems. Further, there may also be side clearance problems which make it desirable that when the hood is in its loading position it not extend very far over the wheel at that side of the spreader chassis. Insofar as the segmented and hinged hoods are concerned, their length and weight generally requires the use of a fairly large stiffening or rigidifying brace that extends the entire length of the hinged part of the hood; and this adds to the cost. In addition, particularly on large spreaders such hinged hood segments are heavy enough to require some sort of a system of levers to move them. Since such levers, or a hydraulic cylinder for moving the cover segments, should be located at only one end of the container, the hinged segments must pivot around heavy torsion tubes.
In addition, the prior art spreader hoods are not adjustable to different positions above the container for spreading material of different characteristics. There is a substantial advantage to being able to so adjust the hood.